Key Takeaways:
- Record-breaking water levels occurred at 31 tidal gauges across the nation, particularly along the Pacific Coast, during the first weekend of January 2026.
- The world’s warming oceans are driving increasing weather extremes, including coastal flooding, more intense hurricanes, and melting ice.
- At least a half-dozen warm temperature records were set on New Year’s Day, following a December that broke or tied nearly 20% of all monthly warm records set or tied in 2025.
- 2025 was the third warmest year on record since measurements began in 1850, with each of the last 11 years among the 11 warmest years on record.
- Ocean heat content continued to set records globally in 2025, with broad ocean warming across basins.
Introduction to the Extreme Weather
January 2026 started with remarkable weather, including record temperatures, dramatic high tides, and news that oceans keep getting warmer. During the first weekend of the new year, record-breaking water levels occurred at 31 tidal gauges across the nation, particularly along the Pacific Coast, according to the National Oceanic and Atmospheric Administration. When the full moon was closest to the Earth on January 4, higher-than-normal tides flooded low-lying areas along the California coast, where heavy rains made the flooding worse in some locations. This extreme weather is not an isolated incident, but rather part of a larger trend of increasing weather extremes driven by the world’s warming oceans.
The Role of Warming Oceans
A key factor driving some of the increasing weather extremes, including coastal flooding, is the world’s warming oceans, said Michael Mann, a climate scientist and professor at the University of Pennsylvania. Mann was one of a group of 55 scientists around the world who co-authored an ocean warming study published on January 9 in the journal Advances in Atmospheric Science. "Both the warming of the oceans and the ocean surface are playing a role in the extreme weather that we continue to see, as warming oceans evaporate more moisture into the atmosphere, driving the record flooding we are seeing, the more intense and damaging hurricanes, and the melting ice, rising sea level and coastal inundation," Mann told USA TODAY. This warming of the oceans is not just a surface-level phenomenon, but rather a deep-seated trend that is driving changes in the Earth’s climate system.
Record-Breaking Temperatures
Meanwhile, at least a half-dozen warm temperature records were set on New Year’s Day, according to NOAA’s National Weather Service. The warmth followed a December that broke or tied so many monthly warm high or overnight warm low temperature records that it accounted for nearly 20% of all the monthly warm records set or tied in 2025. In the Sioux Falls, South Dakota, weather service region, a half-dozen new records were set on January 13, the weather service office reported. The 36-degree overnight low temperature at Sioux Falls was 9 degrees warmer than the normal high temperature for the date and 28 degrees warmer than the normal low. At least four other weather stations in the region reported similar overnight lows that were several degrees warmer than the typical high.
High Tides and Coastal Flooding
Record water levels occurred in some California locations during January’s full moon high tides. In San Francisco, the tide was the fourth highest since records began in 1898. Record high tides were reported in Santa Barbara, Richmond, Martinez-Amorco, and Redwood City. Widespread coastal street flooding occurred in King Salmon and elsewhere along the coast in Humboldt County, California, the weather service said. Flooding also was reported in San Diego. Federal scientists expect such flooding to become more frequent over time with higher sea levels. NOAA’s annual high tide outlook predicts the North Spit location in Humboldt County and San Diego could experience the highest number of flood days along the Southwest Pacific Coast in 2026.
Ocean Heat Content
Ocean heat content continued to set records globally in 2025, with "broad ocean warming across basins," the team of researchers reported in the study Mann participated in. The warming continued "in response to increased greenhouse gas concentrations and recent reductions in sulfate aerosols, reflecting the long-term accumulation of heat within the climate system." Unlike sea surface temperatures that can fluctuate substantially, ocean heat content – which measures the warming below the surface of the ocean over the full ocean depth – shows a very steady warming trend, Mann said. "Though this year was not a new record for global surface temperatures, it was a record for ocean heat content." Each of the past nine years has set a new record, Mann said. In 2025, about 33% of the global ocean area ranked among the top three warmest conditions since records began in 1958, while about 57% was within the top five, their study reported.
Intense Rainfall
A bevy of scientists have reported the warming oceans also help drive more intense rainfall. That’s especially true for the Gulf of America, renamed from the Gulf of Mexico by President Donald Trump, USA TODAY has previously reported. The warming Gulf helps move more moisture northward in an arc up and over the central and eastern U.S. On January 8, La Farge, Wisconsin, was one of more than a dozen locations within the La Crosse weather service region that set new records for 24-hour rainfalls in the month of January. The 2.29 inches of rain in La Farge was more than an inch above the amount of rain the station normally receives during the entire month. This intense rainfall is just one of the many consequences of the world’s warming oceans, and it is likely to become more frequent and severe in the coming years.
